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排序方式: 共有51条查询结果,搜索用时 15 毫秒
1.
J. Javier Gutiérrez J. Carlos Palencia Michael González Harbour 《Real-Time Systems》2014,50(2):230-269
The ARINC-664, Part 7 (AFDX) standard defines a communication network based on Ethernet and the UDP/IP protocols. Contrary to general-purpose Ethernet, the timing behavior in AFDX is deterministic due to the use of special network switches and end systems with static routing tables and traffic policing at the sending end through mechanisms called virtual links. Even though the latencies in this network are bounded, there are scheduling and contention effects that need to be analyzed. In this paper we develop a response-time analysis for multipacket messages transmitted through an AFDX network including the scheduling of the virtual links and sub-virtual links, and also the contention in the end systems and in the switches. This analysis allows us to obtain worst-case latencies and output jitter for the network messages with a precise modeling of the sending and receiving ends. These results can be integrated in a holistic approach with the response time analysis of the threads in the processing nodes to obtain end-to-end response times in heterogeneous distributed systems. 相似文献
2.
S. Lucas E. Gonzlez M.P. Calvo C. Palencia E. Alonso M.J. Cocero 《The Journal of Supercritical Fluids》2007,40(3):462-469
Supercritical impregnation of Radiata pine with ethyl acetate and decanal using CO2 as carrier solvent has been studied at pilot plant scale. Radiata pine is one of the most common wood species that is originally from Australia and is widely grown in Spain and Portugal and ethyl acetate and decanal were selected as organic compounds.Some experiences were carried out to obtain the optimal operating conditions for the supercritical impregnation process. Experiments were conducted at pressures of 7–15 MPa, temperatures of 35–50 °C and solvent flow rate between 1.5 and 3.5 kg/h. The results of this study have indicated that the treatment gives much better preservative penetration and retention operating with low pressures (7.5 MPa), low temperatures (close to 35 °C) and moderate CO2 flow rate (3.5 kg/h) in the selected operating range. Moreover, a simple mathematical model of two adjustable parameters (external mass transfer coefficient and partition coefficient) has demonstrated to fit the experimental impregnation curves with reasonable accuracy (average absolute deviation, 3–10%). 相似文献
3.
Gonzalo Vegas-Sánchez-Ferrero Santiago Aja-Fernández Marcos Martín-Fernández César Palencia 《Mathematics and computers in simulation》2012
A systematic method to deal with the interrelations of systems with multi-index quantities (random variables) is proposed. The method differs of the well-known Polykays. An application of the theoretical results here presented is the calculation of the moments of the sample variance for general populations in a direct way. The main advantage of the proposed methodology is that no conversion formulae and other complicated Polykays rules are needed. However, the proposed method is compatible with Polykays philosophy and conversion formulae and multiplication rules can be derived by using the theoretical results of this work. For practical purposes, two algorithms for the calculation of the moments of the sample variance are proposed. 相似文献
4.
Guillén MD Ibargoitia ML Sopelana P Palencia G Fresno M 《Journal of dairy science》2004,87(2):284-299
The study of the headspace components of fresh smoked goat cheese, was carried out by means of solid-phase microextraction using a polyacrylate fiber followed by gas chromatography/mass spectrometry. The samples studied were six artisan Palmero cheeses manufactured following traditional methods and smoked using pine needles. The cheese regions studied were exterior, interior, and a cross section. In total, more than 320 components were detected, the exterior region being the richest in components, among which were acids, alcohols, esters, hydrocarbons, aldehydes, ketones, furan and pyran derivatives, terpenes and sesquiterpenes, nitrogen derivatives, phenol, guaiacol and syringol derivatives, ethers, and others. In addition to typical cheese components, typical smoke components were also detected; these latter were present especially in the headspace of the exterior region and only those in significant concentrations in the exterior region were also detected in the interior. The main components were acids and phenolic derivatives. These latter compounds play an important role in the flavor of this cheese, and their relative proportions together with the presence of specific smoke components derived from pine leaves may be considered of interest in order to distinguish this cheese from others smoked with different vegetable matter. 相似文献
5.
Electrochemical impedance spectroscopy (EIS) was used to study the fouling produced due to the adsorption of poly(vinyl sulfonic
acid) on polyethersulfone membrane during metal ion recovery by polymer-enhanced ultrafiltration (PEUF). A solution of PVSA
(40 mM in monomeric unit and pH 3.0, 4.5, and 6.0) was placed in a ultrafiltration cell, and then a stream of metal ions (2.0 mM
in Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and Pb2+) was passed from reservoir to cell. Fouled membranes were studied by EIS at low and intermediate frequencies. Measurements
of hydrodynamic permeability and ATR-FTIR spectra were also obtained. Different relaxation processes were observed with characteristic
frequencies (f
0) ~ 78 kHz and f
0 ~ 3562 kHz for active layer and clean membrane, respectively, while the frequencies for the fouled membrane f
0 = ~79.4 and f
0 = ~2511.9 kHz (pH 3.0). The value of f
0 could not be defined at pH 6.0. The relaxation times obtained were in the order of ×10−5 and ×10−3 s approximately for all cases. Our results suggest that relaxation mechanisms, at intermediate frequencies, can mainly be
associated to polarization processes or to the migration of charge carriers. 相似文献
6.
M. Alejandra Mazo Cristina Palencia Andrés Nistal Fausto Rubio Juan Rubio José Luis Oteo 《Journal of the European Ceramic Society》2012,32(12):3369-3378
Dense silicon oxycarbide glasses (SiOC) have been produced by spark plasma sintering (SPS) of SiOC powders. Raw powders were obtained by pyrolysis under nitrogen at 1100 °C of tetraethylorthosilcate/polydimethylsiloxane (TEOS/PDMS) hybrids. SPS experiments were carried out at 1300 and 1500 °C at 10 and 80 MPa and then were studied by chemical analysis, 29Si and 13C MAS NMR, ATR, Raman, XRD, FE-SEM, density, porosity, microhardness (Hv) and thermal conductivity (K). The SiOC materials are formed by SixOC4?x units within a silica matrix where silicon carbide and graphite nanodomains are also present. After the SPS treatment the silicon carbide crystallite size is close to 2.5 nm. At 1300 °C and 1500 °C the carbon nanodomain size is close to 3 nm and 2 nm, respectively. Hv values vary from 3.4 to 9.15 GPa, for 30% and 1% of porosity, respectively. Finally, K is always close to 1.38 W m?1 K?1. 相似文献
7.
M. A. Mazo C. Palencia A. Nistal F. Rubio J. Rubio J. L. Oteo 《Journal of Materials Science》2012,47(13):5169-5180
Carbon nanofibers/glass (CNF/G) nanocomposites were obtained from a glass powder of low melting point and pristine CNFs. Green
bodies containing from 0 to 22 % (v/v) of CNFs were sintered under nitrogen atmosphere in the 550–700 °C temperature range
with different holding times. A fully microstructure characterization, by means of Hg porosimetry and N2 adsorption, was carried out for understanding the CNFs/G composites behavior during the sintering process. This understanding
is required to optimize the microstructural design of CNFs/glass nanocomposite materials. During sintering two different and
simultaneous phenomena occur the matrix crystallization and the pore formation. The glass matrix crystallization temperature
decreases from 650 to 550 °C, when CNFs concentration increases to 22 % (v/v). The glass matrix produces the CNFs degradation
and generates gaseous species which lead to homogeneous or foamy materials. This depends on the CNFs concentration and thermal
treatment conditions. Foamy nanocomposites present pore size distributions with pores <0.1 and close to 20 μm. The glass matrix
wets the CNFs and produce their degradation been of 1 % of carbon loss in all nanocomposites. 相似文献
8.
Russo P López P Capozzi V de Palencia PF Dueñas MT Spano G Fiocco D 《International journal of molecular sciences》2012,13(5):6026-6039
Probiotics, prebiotics and synbiotics are frequently-used components for the elaboration of functional food. Currently, most of the commercialized probiotics are limited to a few strains of the genera Bifidobacteria, Lactobacillus and Streptococcus, most of which produce exopolysaccharides (EPS). This suggests that the beneficial properties of these microorganisms may be related to the biological activities of these biopolymers. In this work we report that a 2-substituted-(1,3)-β-d-glucan of non-dairy bacterial origin has a prebiotic effect on three probiotic strains. Moreover, the presence of this β-d-glucan potentiates in vitro adhesion of the probiotic Lactobacillus plantarum WCFS1 to human intestinal epithelial cells. 相似文献
9.
Enzyme activities (α- and β-glucosidases, α- and β-galactosidases and β-fructofuranosidase) and organic acid production of four strains of lactic acid bacteria (LAB; Streptococcus thermophilus STY-31, Lactobacillus delbrueckii subsp. bulgaricus LBY-27, Lactobacillus casei LC-01 and Lactobacillus acidophilus LA-5) and Bifidobacterium lactis BB-12 were tested on milk and MRS fermentation broth with glucose, lactose or fructooligosaccharides (FOS) as carbon source. The highest β-galactosidase activity was found in L. acidophilus growing on milk. As compared to milk, α-glucosidase activity was increased with FOS by B. lactis, L. acidophilus and L. casei. The analysis of organic acids and short-chain fatty acids in the medium growth showed that lactate and acetate were the major fermentation metabolites produced by LAB and bifidobacteria, respectively. However, a metabolic shift towards more acetate and formate production, at the expense of lactate production, was observed during growth of L. casei on FOS. When grown on FOS as sole carbon source, L. acidophilus showed the highest production of lactate among the species tested. In addition, L. acidophilus demonstrated resistance to colonization against the intestinal pathogens Escherichia coli and Salmonella enterica in competition assays. 相似文献
10.
JamesM. Takacs Suman Layek Hector Palencia RossN. Andrews 《Advanced Synthesis \u0026amp; Catalysis》2005,347(15):1937-1942
An optimized palladium‐N‐heterocyclic carbene catalyst system effects the palladium‐catalyzed bisdiene cyclization‐trapping with phenol at the 0.01% catalyst loading level with a TON of 7.6×103 and TOF of 280 h−1, values much higher than typically found for this and related carbocyclizations. The reaction scales well and the trans‐substituted six‐membered ring product is obtained in excellent yield on a 10‐mmole scale without further optimization of the catalyst system or reaction conditions. 相似文献